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`save_array` rejects anything that is not `NDArrayLike` before it reaches `np.isscalar(arr)`. numpy scalars lack `__len__` and `__setitem__`, so they never pass the protocol check, and the `np.array(arr)` fallback was dead. numpy 2.5.4 changed the `np.isscalar` stub from `TypeGuard` to `TypeIs`, which lets mypy intersect the narrowed `NDArrayLike` with the scalar union and report the branch as unreachable. Delete it and pin the error path. Assisted-by: ClaudeCode:claude-fable-5-1
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save_arrayrejects anything that is notNDArrayLikebefore it reachesnp.isscalar(arr), and numpy scalars never pass that protocol check because they lack__len__and__setitem__, so thenp.array(arr)fallback could never run. This PR deletes the dead branch and adds a test pinning theTypeErrorpath that actually handles scalars.Why now
numpy 2.5.4 changed the
np.isscalarstub fromTypeGuard[...]toTypeIs[...]. ATypeIslets mypy intersect the already-narrowedNDArrayLikewith the scalar union, discover the intersection is empty, and reportStatement is unreachable. That is the lint failure on the upstream dependabot bump zarr-developers/zarr-python#4549, where mypy fails only because the lock moves numpy from 2.5.2 to 2.5.4. The agent bisected it: mypy 2.4.0 with numpy 2.5.2 passes, mypy 2.3.1 with numpy 2.5.4 fails.Verification
uv run --frozen mypypasses on all 203 files under both numpy 2.5.2 (this branch's lock) and 2.5.4 (the dependabot lock).save-related tests intests/test_api.pypass, plus the newtest_save_array_rejects_scalar.No changelog fragment: internal cleanup with no user-visible behavior change.
Stack bookkeeping
Independent of other PRs. Once this lands on upstream main, the dependabot PR 4549 needs a rebase for its lint job to go green.
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